Now neuroscientist and moviemaker Alex Rivest has produced a
new video that illustrates the phenomenon, called airglow. Atoms and molecules,
excited by ultraviolet radiation from the sun, emit light when they return to
their ground state or when they combine due to chemical reactions to create new
molecules. During the day, scattered light from the sun masks this activity, so
it only becomes visible after dark.

Different atoms and molecules are responsible for each colour.
The yellow layer, which is about 5 km thick, is made up of sodium atoms from
broken up meteors that radiate weakly in their excited state. Directly above, a
thinner green band is visible as oxygen and nitrogen combine to form nitric
oxide. A faint blue glow surrounds the green one, made up of excited oxygen
molecules. Higher up, a red layer lurks due to light emissions as ozone
and hydrogen combine to form excited hydroxyl radicals.

The rings are not always uniform due to gravity waves in the
atmosphere.
Like waves in water, they occur when stable layers of different densities are
disturbed and try to regain equilibrium.